Phosphorus production



Sept. 4, 1962 D. E. LouDoN ETAL PHOSPHORUS PRODUCTION INVENTORS DONALD E. LouDoN WARREN C. SCHREINER ATTORNEYS United States Patent Office 3,052,523 Patented Sept. 4, 1962 3,052,523 PHOSPHORUS PRDUCTIQN Donald E. Loudon, New York, and Warren C. Schreiner, East Norwich, NY., assignors to The M. W. Kellogg Company, Jersey City, NJ., a corporation of Delaware Filed Feb. 1, 1960, Ser. No. 5,860 12 Claims. (Cl. 213-223) This invention relates to the production of phosphorus and more particularly, to the production of phosphorus or phosphoric yacid from phosphatic materials. Still more particularly, the invention relates to the production of elemental phosphorus, and subsequently phosphoric acid, from phosphate rock by a novel method of pyrolysis and reduction treatments.

This invention is a continuation-in-part of our prior and co-pending application Serial No. 600,287, filed July 26, 1956, now abandoned, and a continuation-in-part of our prior and co-pending application Serial No. 855,785, filed November Z7, 1959.l

Prior to our invention, phosphoric acid was produced commercially by two principal processes. In the so-called wet process, phosphate rock is digested with sulfuric acid to produce a solution of phosphoric acid containing a suspension of nely divided calcium sulfate. This solution is filtered and then concentrated by evaporation to provide the desired concentration of phosphoric acid. It has been found, however, that the acid produced in this manner is not suitable in instances in which phosphoric acid of a high degree of purity is desired, since it usually contains varying quantities of `deleterious impurities, particularly calcium sulfate. These impurities are especially troublesome where the phosphoric acid is used in cornmercial liquid fertilizers, inasmuch as they tend to form deposits in the nozzles employed for applying the fertilizer. Thus, because of the difficulty encountered in purifying phosphoric acid produced by the wet process for use in liquid fertilizers or other commercial applications, acid produced by this process is seldom employed for the -above purposes.

Another commercial method for the production of phosphoric acid resides in the use of the electric furnace which provides a means for producing elemental phosphorus of an improved degree of purity. In the electric furnace process, elemental phosphorus is produced by the reduction of phosphate rock with metallurgical coke in an electric furnace. Phosphorus thus produced is separated from the furnace gases by condensation, and is then burned to produce phosphorus pentoxide which is hydrated to phosphoric acid. While phosphoric acid produced `by the electric furnace process is of improved purity for such purposes as the preparation of liquid fertilizers and for incorporation in various feed products, it nevertheless has the disadvantage of being extremely expensive to produce by the aforementioned method because of the large quantities of electric power which are required to operate the furnace.

Another method that has been suggested for the production of phosphorus is one in which the phosphate rock is first sintered to make it poro-us in nature so that it might lend itself to an impregnation treatment for the deposition of carbon thereon. Thereafter, the phosphate rock is coated by cracking a hydrocarbon in its presence, and then, the phosphate material is heated in order to reduce it to the elemental phosphorus. In this process, a fixed bed operation is employed. The d-iiiiculty encountered in carrying out this method, however, resides in the fact that there is obtained a coalescence or sticking of 4the phosphate rock particles in both the cracking or pyrolysis zone and also in the subsequent reduction zone. This coalescence of the phosphate rock particles results in the inabiliity to obtain a substantially complete carbon coating of the rock particles so that they may be subsequently effectively reduced. Furthermore, the subsequent coalesceuce in the reduction zone also renders it impossible to carry out the substantially complete reduction of the coated phosphate rock to produce elemental phosphorus in a high yield. Hence, prior to our invention, no satisfactory method has been obtained for the efficient and economic production of elemental phosphorus from phosphate rock or from phosphatic materials.

It is, therefore, an object of this invention to provide an improved process for the production of phosphorus.

Another object of the invention is to provide an improved process for the production of elemental phosphorus from phosphate rock or other phosphatic material.

Still another object of the invention is to provide an improved process for the production of elemental phosphorus, and subsequently phosphoric acid, in an efficient and economical manner and in a high yield.

Other objects and advantages inherent in the invention will become apparent to those skilled in the art from the accompanying description land disclosure.

ln accordance with the present invention, a novel l rocess has been provided for the production of phosphorus, as more fully hereinafter discussed, which comprises, in general, a two-stage method of applying a fluidized technique to effectively deposit carbon on the phosphate rock particles in such manner that there is obtained no coalescence of these particles, or a reduction of the rock in a cracking or pyrolysis Zone; and thereafter, the thus-coated rock particles are heated in a reduction zone at substantially high temperatures at which the phosphate rock particles would otherwise coalesce but for the coating or carbon thereon, to effect a reduction of the phosphate rock, with the production of elemental phosphorus, as a product of the process. The critical features of the present process, as more fully hereinafter discussed, reside in the specific temperature conditions which are maintained in the pyrolysis and in the reduction zones, and in the presence of a critical quantity of silica in the phosphate rock particles undergoing treatment to permit reduction of the fluidized coated rock particles to occur at the temperatures maintained in the reduction zone.

Specifically, the above results are obtained by iiowing a uid hydrocarbon through a pyrolysis or cracking zone which contains a mass of finely divided phosphate rock particles in order to maintain these particles in a fluidized condition, and also as a source of car-bon for effecting a coating of the phosphate rock particles. The temperature maintained in this pyrolysis or cracking zone is such as is effective to cause crack-ing of the fluid hydrocarbon with the deposition of carbon on the rock particles, but below the temperatures at which these particles would coalesce and at which they would be reduced to phosphorus. In this respect, it has been found that a ycriticality of the `operating temperatures employed exists with respect to the relationship of the coating operation conducted in the pyrolysis zone and that of the subsequent operation conducted in the reduction zone. It has been found, in uidized operations, that the mere coating of the phosphate -rock particles with carbon does not, in each instance, satisfy the requirements for carrying out a successful reduction operation in the reduction zone, in order to obtain elemental phosphorus in good yield. In this respect, it has been found that if the coating operation `is conducted at a temperature below approximately 1400" F., in the pyrolysis zone, insufficient carbon is laid down on the rock particles to make subsequent reduction possible from a practical standpoint. On the other hand, if the coating operation in the pyrolysis zone is conducted at a temperature above approximately 2l00 F., the carbon, coating the rock particles, is not rendered sufficiently |reactive for subsequent reduction to take place in the reduction zone at temperatures necessary to maintain iluidized conditions. Thus, it has been found that the temperatures maintained, for effectively carrying out the coating operation in the pyrolysis zone, under fluidized conditions, are between about 1400D F. and about Zl F. Optimum results, from an economic standpoint, are obtained by conducting the cracking of the Huid hydrocarbon at temperatures between about 1750 F. and about 1950 F.

In carrying out the subsequent reduction treatment under fluidized conditions, it has been found that the reduction zone must be maintained at a temperature of at least approximately 2200" F. If the reduction op-eration is conducted at a temperature below approximately 2200 F., the reduction proceeds at such a low rate that for practical purposes no appreciable quantities of elemental phosphorus are obtainable. On the other hand, if the reduction operation is conducted at a temperature above approximately 2600u F., uidization conditions are difcult to maintain because of the relatively high temperatures that are utilized. Thus, it has been found that operable temperatures to be maintained in the reduction zone for effectively carrying out the reduction operation, under fluidized conditions, are between about 2200 F. and about 2600 F. The optimum results, from an economic standpoint, are obtained by conducting the reduction operation at temperatures between about 2300 F. and about 2500" F. From the above, it will become apparent that the relationship of the temperature conditions maintained during the coating operation, which is `conducted in the pyrolysis zone, is critical and of prime importance with respect to the temperature conditions maintained in the subsequent reduction treatment, where the pyrolysis and the reduction treatments are each sought to be carried out under fluidized conditions. The pressure which is maintained in both the cracking and the reduction zones is preferably between about 0 and about p.s.i.g. The actual operating conditions employed, will, of course, be dependent on many factors and may vary widely Within the above ranges, without departing from the scope of the invention. It will be noted, furthermore, that by operating within the ranges indicated above, the coalescence of the coated phosphate rock particles within the reduction zone, which would otherwise take place except for the coating of carbon thereon, is avoided and elemental phosphorus is readily produced as a product of the process.

The phosphate rock, which is employed as the starting material in accordance with the present invention, will normally be in the form of fluoroapitite, Ca1O(PO4)6F2. This phosphate rock -Will normally contain varying quantities of other substances, such as aluminum oxide. Suitable phosphate rock is found, for example, incertain parts of Florida, Tennessee and Idaho, as well as in various other locations both in the United States and abroad. The phosphate rock, which is employed in the process of the present invention, should be in a range of particle sizes suitable for uidization, so that the process can be carried out by maintaining uidized beds in the respective cracking and reduction zones. Particles having an average diameter from about 30 microns to 1A inch, more usually, between about 100 to about 150 mesh, are normally preferred. However, rock particles of other sizes which `can be subjected to iluidization may also be employed without departing from the scope of the invention. The hydrocarbon which is employed in carrying out the cracking operation, as indicated above, is in the fluid state, i.e., it may be a gaseous or liquid hydrocarbon. Preferably, the hydrocarbon is employed in the form of a normally gaseous hydrocarbon or a gaseous material, such as natural gas (methane) containing substantial quantities of one or more normally gaseous hydrocarbons. The fluidized gas employed yin the reduction zone may vcomprise nitrogen, hydrogen and mixtures of hydrogen and methane.

In a preferred embodiment of the invention, the uidized bed in the cracking zone preferably has a density between about 25 and about 30 pounds per cubic foot, and a superficial linear gas velocity between about 0.5 and about 2 feet per second. The density of the uid bed in the reduction zone is preferably between about 25 and about 35 pounds per cubic foot, and the superficial linear gas velocity is preferably between about 0.4 and about 2 feet per second. The average residence time of the uid hydrocarbon in the cracking zone is preferably between about 10 and about 60 seconds, while the residence time of the coated phosphate rock particles in the reduction zone is preferably between about 1 and about 8 hours, when the preferred temperatures are employed. In general, it is preferred to preheat the fluid hydrocarbon, usually to about 1000 F., before being introduced into the cracking zone. It will be understood, of course, that the velocities, densities and residence times, stated above, may be employed outside of the preferred ranges, without departing from the scope of the invention. If desired, additional gas, or other fluidizing media, may be injected into the system, wherever necessary, to aid in transporting the tluidized material wit-hin the process, or as a fluidizing or stripping gas.

The operating conditions described above are such as will result in obtaining a high degree of cracking of the fluid hydrocarbon in the cracking or pyrolysis zone, with substantially no reduction of the phosphate rock particles taking place within this zone. The particles of phosphate rock which thus become coated with carbon, are then transferred to the reduction zone, Where the above-described conditions are adapted for the eficient reduction of the phosphate rock, employing the deposited carbon as the reducing agent. It has been found that by producing carbon, within the cracking zone, and allowing it to become deposited on the individual particles of the phosphate rock, as described above, there is little or no tendency for the rock particles to agglomerate or stick. In this connection, it will be noted that if the particles of phosphate rock would otherwise tend to agglomerate, the equipment would become completely fouled by slag and would be incapable of operating for any substantial length of time. Particles of phos phate rock, which are not coated with carbon, have been found to exhibit a strong tendency to coalesce at the above-mentioned reduction temperature, In order to insure that agglomeration or sticking of the phosphate rock particles does not take place, it is preferred to operate the process under conditions such that carbon is produced in some excess of the amount actually required to be deposited lfor complete reduction to take place of the calcium phosp-hate to phosphorus and carbon monoxide.

Theoretically, the reaction which is carried out in the reduction zone may be represented as follows:

In this respect, it has been found that the presence of silica, in the phosphate rock, as more fully hereinafter discussed, fluxes the rock particles so that the actual reaction which probably takes place may be represented as follows:

The above reactions have only been indicated for purposes of explanation, and it should be understood that the process of the present invention is not necessarily limited to these systems in which the above reactions take place.

Apart from the critical requirements of the present process, in which the specific temperature conditions described above must be maintained in the pyrolysis and reduction zones, a further critical requirement resides in maintaining a specific quantity of Silica in the phos phate rock particles undergomg treatment. In this re- 5. spect, it has been found that the presence of silica in the rock particles is necessary so that the silica may react with the lime (CaO), resulting from the reduction of the calcium phosphate, to flux the rock particles and to permit the reduction to occur at relatively high rates at the above-mentioned temperatures maintained in the reduction zone under iluidized conditions. For this purpose, it has been found that a silica to lime ratio of at least 0.2 by Weight must be present. For optimum results, silica to lime ratios of about 0.2 to about 1.5 by weight are generally preferred. The silica, required to be incorporated in the rock, may be in any suitable form, e.g., in the form of silicon dioxide, in the quantity desired.

The above-mentioned pyrolysis and reduction treatments of the phosphate rock particles, may be carried out in several ways. -In accordance with one modication of the present process, a mass of phosphate rock is introduced into a reaction zone which is equipped with heat exchange means adapted to permit the passage of gaseous combustion products, e.g., ue gas, therethrough. The mass of phosphate rock is then passed into the reaction zone into contact with the heat exchange means. A fluid hydrocarbon, e.g., methane, is then introduced upwardly into the cracking zone or pyrolysis Zone, and into contact with the mass of the phosphate rock particles. The heat exchange means in the pyrolysis zone is maintained at a temperature which is sufficient to heat the phosphate rock particles to a temperature within the aforementioned range of about 1400J F. to about 2.100a F. so that the hydrocarbon is cracked and carbon thusformed will coat the phosphate rock particles, which temperature is below the level at which the phosphate rock particles would otherwise coalesce. Thereafter, the coated phosphate rock particles are passed to the reduction zone in which they are heated at a temperature within the aforementioned range of about 2200 F. to about 2600 F. to reduce the phosphate rock and to produce elemental phosphorus. This modification is more fully described in our aforementioned co-pending application Serial No. 600,287, and is therefore believed to require no further elaboration.

fIn another modification of the improved process of the present invention, preheated inert solids are introduced into the cracking or pyrolysis zone to come into contact with the iluidized mass of phosphate rock particles, to maintain this mass at the desired temperature which is effective to cause cracking of the fluid hydrocarbon with deposition of carbon on the phosphate rock particles. Following the aforementioned cracking treatment, the coated phosphate rock particles are also contacted with preheated inert solids in the reduction zone to heat these coated particles to a temperature within the aforementioned reduction temperature range to reduce the coated particles and to produce elemental phosphorus as a product of the process. A more complete description of this modification of the present process is described in our co-pending application Serial No. 855,785, which also includes additional modifications of this method, and is believed to require no further elaboration. These latter modifications, as set forth in ySerial No. 855,785 include utilization of flue gas from the process as a source of heat for preheating the aforementioned inert solids in either or both the cracking and reduction zones; and also include the modification of introducing a mass of finely-divided phosphate rock into the cracking zone together with a fluid hydrocarbon as a carrier and as an additional source for carbon production. Another portion lof the fluid hydrocarbon is flowed upwardly into the cracking Zone to maintain the phosphate rock in a fluidized condition, and also to act as a primary source for depositing carbon on the rock particles. An additional modification resides in combining the above two modifications in which flue gas is employed as a source for heating inert solids, and the Yfluid hydrocarbon is employed in a dual capacity of acting as a carrier and also as a source for depositing carbon upon the rock particles.

For a better understanding of the process of the present invention, reference is had to the accompanying drawing which is a diagrammatic illustration, in which equipment is shown in elevation, of a suitable arrangement of apparatus for carrying out a preferred embodiment of the invention.

In the drawing, solid feed material is introduced into the system through conduit 11 into a hopper 12, thence through valve 13 and into conduit 14. This solid feed material comprises phosphate rock particles to which silica has been added. This feed material has the composition shown in Table I. In Table I, the elements present have been assumed, for convenience, to be chemically combined as shown, since such chemical combinations are typical, and -it is Inot intended that these chemical combinations necessarily represent the actual combinations present in all lfeed materials. Thus, for example, although phosphorus is represented as being present in the combined form of phosphorus pentoxide, it may actually be present in the combined lform of calcium phosphate.

TABLE I Prior to being introduced into hopper 12, the feed material has been reduced to a particle size in the range from about to about 150 mesh, so that it may be readily fluidized in the process. The solid feed material enters the process at the rate of 90,433 pounds per hour, of which 85,935 pounds per yhour are phosphate rock and 7,083 pounds per hour are added silica.

The phosphate rock and silica entering through conduit 1'4 is picked up by natural gas in conduit 15. The natural gas has the composition shown in Table II and enters conduit 14 through conduit 15 at the rate of 2,695 pounds per hour.

TABLE II Composition of Natural Gas Feed Component: Weight percent CH.,l 92.35

C2 hydrocarbons 2.19

C3 hydrocarbons 0.55

C4 hydrocarbons 0.13

N2 hydrocarbons 4.78

23,500 pounds per hour (1379.6 mols per hour) of this natural gas enters conduit 1'6, while the remainder continues through conduit 15 to pick up the solid material from conduit 14 in a suspension. The gas containing suspended finely divided feed material i-n conduit 14 passes through a heat exchanger 17 where the suspension is heated to a temperature of 1200 F., and then continues through conduit 14 to a pyrolysis reactor 18, which contains a reaction section 19. The feed material entering reactor 18 through conduit 14 is maintained in a uiclized bed in reaction section 19 as a lower dense phase in a pseudo-liquid condition `and an upper dilute phase with an interface 20 between them. The feed material from conduit 14 enters the dense phase of the uid bed in reaction section 119 just below the interface 20. The temperature of the fluidized bed in reactor 18 is maintained at about 1800L7 F., while the density of the dense phase of the bed is 31.7 pounds per cubic foot (not including the shot used for heating, as described below) and the bed height is 40 feet. The material in reaction section 19 of reactor 18 is maintained in a fluidized condition by the upward low of natural gas obtained from conduit 16 at a superficial linear gas velocity of 1.25 feet per second. Prior to being injected into the uidized bed in reactor 18, the natural gas in conduit 16 has been heated to a temperature of 1200 F. in a heat exchanger 21. The pressure at the top of reaction section 119 of reactor 18 is maintained at 9.8 p.s.i.g., while the pressure at the bottom of the uidized bed is 17.7p.s.i.g. Heat is supplied to the uidized bed in reactor 18 by the use of heated inert solids, which are introduced into reactor 18 through a distributor section 22 via a plurality of distributing pipes 23. Prior to the introduction into reactor 18, as indicated above, the solid inert material is lfirst introduced, via l-ine 24, into burners 25, in which it is heated by the combustion of tail gases, introduced into burners 25 via line 26. Burners 25 are maintained at a pressure of 1.0 p.s.i.g. The equilibrium temperature in burners 25 is maintained at 2280 F., while the rate of introduction of the unheated solid inert material, via lines 24, is maintained at 410,000 pounds per hour -in each line. Air, employed in the combustion of tail gases in burners 25 enters the process through conduit `27 at the rate of 460,688 pounds per hour.

Following the combustion of the abovedescribed tail gases, the heated inert solid material is then passed Via conduits 28, with the products of combustion into separator 29, in which the heated solid material is disengaged from the products of combustion. Separator 29 is maintained at a temperature of 2280 F. and a pressure of 0.5 p.s.i.g. The separated products of combustion are withdrawn from separator 29 via line 30 and removed from the process. After being introduced into the reaction section 19 of reactor 18, and after the cracking operation has taken place, the hot inert solid material (or hot-shot) passes through the uidized bed and is separated at the bottom of reactor 18 in section 31. The pressure within the fluidization zone is maintained at 17.7 p.s.i.g., While the pressure at the point where the spent inert solids leave the reaction section is at 22.0 p.s.i.g. The spent heated inert solid material 4is then withdrawn fromy reactor 18 through conduit 32 into a receptacle 33, the rate of flow being controlled by valve 34. The spent inert material is then ready for re-use.

As was indicated above, the air employed for combustion of tail gas in burners 25, enters the process through conduit 27 at the rate of 460,688 pounds per hour. Of this amount, 125,299 pounds per hour are passed, via pump 35, to burners 25, as previously described. Of the remaining quantity of air in line 27, 299,135 pounds per hour are transferred into line 36, via pump 37, for subsequent use, as described below. The remaining quantity of 36,254 pounds per hour is transferred into line 38, via pump 39, tobe used as is also hereinafter described.

The average residence -time of the gas in reactor 18 is Iabout 40 seconds. The operating condtiions maintained in reactor 18 are such that about 50 percent of :the methane in the natural gas is cnacked to produce carbon and hydrogen. The carbon thus produced adheres to ythe individual particles of solid material present in the reraotion zone and results in these panticles becoming heavily coated wtih carbon. Fluidized particles of solid material coated with carbon are withdrawn from reactor -18 through a standpipe 40 and are passed through valve 41 to a reduction reactor 42.

163 pounds per hour of nitrogen enters the system through conduit 43, and 117 pounds per hour of this nitrogen continues through conduit 43 and is injected into the material in standpipe 40, while the remainder continues through standpipe 44 to he used as explained below. A portion of the gaseous product from reactor 8 18 is Withdrawn through conduit 45 at the rate of 4,414 pounds per hour and passed to the lower portion of reactor 42, where it is used to help maintain a uid bed of iinely divided solids and as a source of carbon in reactor 42. The remaining pontion ofthe gaseous product from reactor '18 is withdrawn through conduit 46, cooled in heat exchanger 17, returned to burners 51 and thus constitutes a source :of fuel for subsequent combustion in these burners.

In reactor 42, the uidized phosphate rock coated with carbon is maintained at a temperature of 2300 F. for an average residence time of about 6 hours. The upper portion of reactor 42 is maintained at -a pressure of 2 psig., while the lower portion is maintained at a pressure of 4.9 p.s.i.g. Under these operating conditions, the carbon adhering to the particles of phosphate rock serves to reduce the phosphate rock and to produce phosphorus. The fluid bed in reactor `42 has a lower dense phase in a pseudo-liquid condition `and an upper dilute phase with an interface 47 therebetween. The `dense phase of the fluidized bed in reactor 42 has a height of 20 feet and an average density of 21.2 pounds per cubic foot (not including the `shot used for heating, as described below). The supercial linear gas velocity of .the gas in reactor 42 is I1.5 feet per second.

The 'temperature of the iluidized bed in reactor 42 is maintained at lthe desired level by circulating heated shot or inert solids, similar to ythat employed in reactor 18. The shot used for such purposes comprises a suitable refractory material, such as `silicon carbide, silicon nitride, or others previously described, and has an average diameter of about 1/16 inch. The heated shot is introduced into reactor 42 through a distributor section 48, vi-a a plurality of distributing pipes 49. Prior to its introduction into reactor 42, `as indicated above, the shot is first introduced via line 50, into burners 51, in which it is heated by the combustion of tail gas or gaseous product from reactor 18, previously described, introduced through line 46. Burners 51 are maintained `at :a pressure of 2.0 p.s.i.g. The equilibrium temperature in burners 51 is maintained at 2550 F., while the rate of introduction of the shot via line 50 is maintained at 1,640,000 pounds per hour to each burner. Air, employed in fthe combustion of tail gases in burners 51 enters the process through conduits 52 4at the rate of 143,738 pounds per hour to each burner.

Following the combustion of the above-described tail gases, the heated inert solid material or shot is passed, via conduits 53, together with the products of combustion into separator 54, in which Ithe heated solid material is disengaged from the products `of combustion. Separator 54 is maintained at a temperature `of 2550 F. and a pressure of 1.5 psig. The separated products of combustion are Wtihdrawn from separator 54 vi-a line 55. This ue gas in conduit 55 is cooled to a temperature of 1970" F. in steam generator 56 and is removed from the process Vthrough conduit 63. Boiler feed water in steam drum 57 is introduced through conduit 58 via pump 59 at .the rate of 54,810 pounds per hour. From steam drum 57, the resulting steam product is withdrawn through line 60 at the rate of 52,100 pounds per hour. Bart of the feed water from steam drum 57 is removed from the system through conduit 61 -at the nate of 2,610 pounds per hour to prevent the build-up of solids. The remainder, together with recycle water, is transferred via conduit 62 into steam generator 56 and the resulting steam-Water mixture is returned to drum 57 via line 93. The total flue gas product from steam generator 56 is wtihdrawn via conduit 63.

Referring now to reactor 42, the pressure within the uidization Zone, as was previously indicated, is maintained at 4.9 p.s.i.g. The pressure sat the point where the spent shot or inert solids leave the reaction section is at 8.4 p.s.i.g. These spent solids are then withdrawn from reactor 42 through conduit 64 into receptacle 65, the

rate of ow being controlled by valve 66. The spent inert material is then ready for re-use, as described above. Air employed for transporting the spent inert materials from reactor 42 to reactor 18 to burners 25 and 51, respectively, is introduced through conduits 67 and 68, respectively, via l-ine 38. ln conduit 67, air is introduced iat the rate of 9540 pounds per hour, and i-n conduit 68, air is introduced at the rate of 26,600 pounds per hour.

The gaseous product from reactor 42 is withdrawn through conduit 69 at the rate of 31,969 lpounds per hour. This gaseous product is then transferred via conduit 69 into heat exchanger 21 where it is cooled to a temperature of 680 F. From heat exchanger 21, the gaseous product material enters a conventional cyclone separator 70, in which entr-ained solid material is separated. The solid material recovered in cyclone separator 70 is withdrawn through conduit 71, passing through valve 72 and is returned to reactor 42 via line 73. Gaseous product material is withdrawn from cyclone separator 70 through conduit 74. This material has the composition shown in Table III.

TABLE III Composition of Gaseous Product Material in Conduit 74 Component: Mol percent CH.1 6.5 C2-C4 hydrocarbons 0.2

From conduit 74, ythe product gas is transferred into a scrubber 75. In scrubber 75, this product gas is scrubbed by la spray of water, introduced through line 76 to condense the phosphorus product. This cooling water is i-ntroduced into `scrubber 75 at the rate of 500,000 pounds per hour and at `a temperature of 149 F. Spray liquor and condensed phosphorus lis withdrawn from .the bottom of scrubber 75 through conduit 77 from which the phosphorus product may be separated i om water by settling action, `or other conventional separating means, as a product of the process, and the water returned to scrubber 75.

Tail gas is withdrawn from the top of scrubber 75 through conduit 7S at a `temperature of 150 F. This tail gas, thus withdrawn from `scrubber 75, has the composition shown in Table IV.

TABLE IV Composition of Tail Gas in Conduit 78 From conduit 78, the tail gas is passed into a gas suction Vessel '79, maintained at a pressure of 0.5 p.s.i.g. This product tail gas is then withdrawn from vessel 79 through conduit 80 where it is pumped into conduit 26, Via pump 81, for re-use in burners 25. The tail gas transferred through conduit 26 yis passed -at the rate of 31,565 pounds per hour.

The spent inert material, or shot, from reactor 42 is withdrawn through conduit 82. This material is then passed through conduit 82 to a shot separator or elutriator 83. In Vessel 83 elutriation is carried out by the transfer of air from conduit 36 via conduit 84 at the rate of 11,660 pounds per hour. The flow of air is controlled by valve 85. The spent shot from vessel 83 is returned to rseparator' 29 through conduit 86. The solid residue from vessel 83` is transferred through conduit -87 to a conventional cyclone separator 88. Cooling water is also introduced linto conduit `87 via conduit 89. ln separator 88, air is withdrawn through conduit 90, while slag is withdrawn through conduit 91 yand -is controlled by valve 92. The slag in conduit 91 has the composition shown in Table V.

TABLE V Composition of Slag in Conduit 91 It should be understood that Tables I through V do not in all cases represent the exact chemical compounds present. In some instances, as previously mentioned, they are intended to represent only the proportions of elements present and these elements are not necessarily chemically combined in the manner indicated.

The embodiment of the present invention `shown in the drawing is not intended to be limited to the particular arrangement of apparatus shown, `and may be practiced with any suitable arrangement of yapparatus and under lany suitable operating conditions. Additional process steps for the preparation of the materials used or for purification or other treatment of the product may, lof cour-se be used. It should be especially noted that the method shown for recovering the elemental phosphorus from the effluent of the reduction reactor is intended for purposes of illustration only, `and that other methods may be employed without departing from the scope `of the invention.

We claim:

1. A process for lthe production of phosphorus which comprises: owing a fluid hydrocarbon through a cracking Zone containing a mass of finely divided phosphate rock to maintain said phosphate rock in -a fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at a temperature not higher than 2l00 F. effective to cause cracking of hydrocarbon with deposition of carbon on `said phosphate rock; passing a gas upwardly through -a mass of carboncoated phosphate rock thus obtained in a reduction lone to maintain said carbon-coated phosphate rock in a fluidized state; and heating the uidized phosphate rock in said reduction zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in a ratio of at least 0.2 at a temperature -above about 2200 F. `and higher than that employed in said cracking zone to effect reduction of said phosphate rock with the production of elemental phosphorus.

2. A process for the production of phosphorus which comprises: flowing a fluid hydrocarbon through a cracking zone containing a mass of finely divided phosphate rock to maintain said phosphate rock in a uidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain -it at a temperature not higher than 2100 F. effective to cause cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carboncoated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a uidized state; land heating the iluidized phosphate rock in said reduction zone without lsubstantial coalescence of said l l coated particles in the presence of silica and calcium oxide in a ratio between about 0.2 and about 1.5 at a tempera- Iture above about 2200 F. land higher than that employed in said cracking zone to effect reduction of said phosphate rock with the production of elemental phosphorus.

3. A process for the production of phosphorus which comprises: flowing a fluid hydrocarbon through a cracking Zone containing a mass of finely divided phosphate rock to maintain said phosphate rock in la fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at a temperature between about l400 F. and 2l00 F. effective to cause cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction Zone .to maintain said carbon-coated phosphate rock in a fluidized state; and heating the fluidized phosphate rock in said reduction zone without substantial coalescence of said coated particles in the presence of silic-a and calcium oxide in -a ratio of at least about 01.2 at a temperature ybetween about 2200 F. and about 2600 'F. and higher than that employed in said cracking zone to effect reduction of said phosphate rock with the production of elemental phosphorus.

'4. A process for the production of phosphorus which comprises: flowing a fluid hydrocarbon through a cracking zone containing a mass of finely divided phosphate rock to maintain said phosphate rock in a fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at a temperature between `abou-t 1750 and about 1950o F. effective to cause cracking of hydroc-arbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone 4to maintain said carbon-coated phosphate rock in a fluidized state; and heating the fluidized phosphate rock in said reduction zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in a ratio of at least 0.2 at a temperature between about 2300 F. and about 2500" F. to effect reduction of said phosphate rock with the production of elemental phosphorus.

5. A process for the production of phosphorus which comprises: flowing a fluid hydrocarbon through a cracking zone containing a mass of finely divided phosphate rock to maint-ain said phosphate rock in a fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at a temperature between about 1750 F. and about 1950 F. effective to cause cracking of hydrocarbon with deposition of carbon lon said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; and heating the fluidized phosphate rock in said reduction zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in a ratio between about 0.2 and about 1.5 at a temperature between about 2300io F. and about 2500 F. to effect reduction of said phosphate rock with the production of elemental phosphorus.

6. A process for the production of phosphorus which comprises: introducing a mass of finely divided phosphate rock and a first portion of a fluid hydrocarbon into a cracking zone; flowing a second portion of a fluid hydrocarbon upwardly into said cracking Zone to maintain said phosphate rock ina fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at a temperature not higher than 2100 F. effective to cause cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; and heating the fluidized phosphate rock in said reduction zone without substantial coalescence of said coated partil2 cles in the presence of silica and c-alcium oxide in a ratio of at least 0.2 at a temperature above about 2200" F. and higher than that employed in said cracking zone to effect reduction of said phosphate rock with the production of elemental phosphorus.

7. A process for the production of phosphorus which comprises: introducing a mass of finely divided phosphate rock and a first portion of a fluid hydrocarbon into a cracking zone; flowing a second portion of a fluid hydrocarbon upwardly into said cracking zone' to maintain said phosphate rock in a fluidized condition; heating said fluidized mass of phosphate rock in said cracking Zone to maintain it at a temperature between about 1400 F. and 2100 effective to cause cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; -and heating the fluidized phosphate rock in said reduction zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in a ratio between about 0.2 and about 1.5 at a temperature between about 2200 F. and `about 2600 F. to effect reduction of said phosphate rock with the production of elemental phosphorus.

8. A process for the production Vof phosphorus which comprises: introducing a mass of finely divided phosphate rock and a firs-t portion of a fluid hydrocarbon into a cracking zone; flowing a second portion of a fluid hydrocarbon upwardly into said cracking zone to maintain said phosphate rock in a fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at a temperature between about 1750 F. and about 1950o F. effective to cause cracking of hydrocarbon with deposition 4of? carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; and heating the fluidized phosphate rock in said reduction Zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in `a ratio between about 0.2 and about 1.5 at a temperature between about 2300" F. and about 2500 F. to affect reduction of said phosphate rock with the production of elemental phosphorus.

9. A process for the production of phosphorus which comprises: flowing a fluid hydrocarbon through a cracking zone containing a mass of finely divided phosphate rock to maintain said phosphate rock in a fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at -a temperature not higher than 2100 F. effective to cause cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly thorugh a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; heating the fluidized phosphate rock in said reduction zone without substantial coalescence of said coated particles in the presence `of silica and calcium oxide in a ratio of at least 0.2 at a temperature above about 2200 F. and higher than that employed in said cracking zone to effect reduction of said phosphate rock with the production of elemental phosphorus; withdrawing a gaseous product from said cracking zone comprising phosphate rock and flue gas; separating flue' gas from phosphate rock thus withdrawn; and employing flue gas thus separated as a source of heat for maintaining the temperature in said cracking zone.l

l0.l A process for the production of phosphorus which comprises: flowing a fluid hydrocarbon through a cracking zone containing a mass of finely divided phosphate rock to maintain said phosphate rock in a fluidized condition; heating said fluidized mass of phosphate rock in said cracking zone to maintain it at a temperature not higher than 2100 F. effective to causeI cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; heating the uidizing phosphate rock in said reduction Zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in a ratio between about 0.2 and about 1.5 at a temperature above about 2200a F. and higher than that employed in said cracking Zone to e`ect reduction of said phosphate rock with the production of elemental phosphorus; withdrawing a gaseous product from said cracking zone comprising phosphate rock and tiue gas; separating ue gas from phosphate rock thus withdrawn; and employing ue gas thus separated as a source of heat for maintaining the temperature in said cracking zone.

11. A process for the production of phosphorus which comprises: flowing a fluid hydrocarbon through a cracking zone containing a mass of -nely divided phosphate rock to maintain said phosphate rock in a fluidized condition; heating said fluidized mass of phosphate `rock in said cracking Zone to maintain it at a temperature between about 1400 F. and 2100 F. effective to cause cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; heating the uidized-phosphate rock in s-aid reduction zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in a ratio between about 0.2 and about 1.5 -at a temperature between about 2200 F. and `about 2600 F. and higher than that employed in said cracking zone to etect reduction of said phosphate rock without the production of elemental phosphorus; withdrawing a gaseous product from said cracking zone comprising phosphate rock and flue gas; separating flue gas from phosphate rock thus withdrawn; and employing flue gas thus separated as a source of heat for maintaining the temperature in said cracking zone.

12. A process for fthe production of phosphorus which comprises: owing a uid hydrocarbon through a cracking zone containing a mass of iinely divided phosphate rock to maintain said phosphate -rock in a lluidized condition; heating said uidized mass of phosphate rock in said cracking zone to maintain it at a temperature between about 1750 F. and about 1950 F. eiective to cause cracking of hydrocarbon with deposition of carbon on said phosphate rock; passing a gas upwardly through a mass of carbon-coated phosphate rock thus obtained in a reduction zone to maintain said carbon-coated phosphate rock in a fluidized state; heating the fluidized phosphate rock in said reduction zone without substantial coalescence of said coated particles in the presence of silica and calcium oxide in a ratio between about 0.2 and about 1.5 at a temperature between about 2300 F. and about 2500 F. to effect reduction of said phosphate rock with the production of elemental phosphorus; withdrawing 'a gaseous product from said cracking zone comprising phosphate rock and flue gas; separating flue gas from phosphate neck thus withdrawn; and employing flue gas thus separated as a source of heat yfor maintaining vthe temperature in said cracking zone.

References Cited in the le of this patent UNITED STATES PATENTS 1,422,699 Guernsey et al July 11, 1922 1,818,662 Weigel et al Aug. 11, 1931 1,841,071 Waggaman et al. Ian. 12, 1932 1,867,239 Waggaman et al. July 12, 1932 2,897,057 Burgess July 28, 1959 2,967,091 Robertson Ian. 3, 1961 FOREIGN PATENTS 378,226 Great Britain Aug. 11, 1932 OTHER REFERENCES Fluidization in Chem. Reactions, Kalbach, pages 105408, Chem. Engineering, January 1947.

Fluid Solids, page 306, Journ. of Chem. Ed. (Ad. See), vol. 24, #6, June 1947.

Fluidized Solids, pages 219, 220, 227-231. Chem. Eng., May 1953.

UNITED STATES PATENT oEEIoE CERTIFICATE 0F CORRECTION Patent No, 3,052,523 September 4, .1962

Donald E., Loudon et al It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as Corrected below.

a Column 2, line 33, for "or" read of --g column 9, llne 56, for "C2-H4 read C2434 --g column lO, line 54,v for.)l "lone" read zone Column I3, line 34, for "wlthout", read with SignedY and sealed this 20th day of August 1963,

(SEAL) Attest:

ERNEST w. SWTDEE DAVID L- LADD Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE PRODUCTION OF PHOSPHORUS WHICH COMRPRISES: FLOWING A FLUID HYDROCARBON THROUGH A CRACKING ZONE CONTAINING A MASS OF FINELY DIVIDED PHOSPATE ROCK TO MAINTAIN SAID PHOSPHATE ROCK IN A FLUIDIZED CONDITION: HEATING SAID FLUIDIZED MASS OF PHOSPHATE ROCK IN SAID CRACKING ZONE TO MAINTAIN IT AT A TEMPERATURE NOT HIGHER THAN 2100* F. EFFECTIVE TO CAUSE CRACKING OF HYDROCARBON WITH DEPOSITION OF CARBON ON SAID PHOSPHATE ROCK: PASSING A GAS UPWARDLY THROUGH A MASS OF CARBONCOATED PHOSPHATE ROCK THUS OBTAINED IN A REDUCTION LONE TO MAINTAIN SAID CARBON-COATED PHOSPHATE ROCK IN A FLUIDIZED STATE; AND HEATING THE FLUIDIZED PHOSPHATE ROCK IN SAID REDUCTION ZONE WITHOUT SUBSTANTIAL COALESCENCE OF SAID COATED PARTICLES IN THE PRESENCE OF SILICA AND CALCIUM OXIDE IN A RATIO OF AT LEAST 0.2 AT A TEMPERATURE ABOVE ABOUT 2200* F. AND HIGHER THAN THA T EMPLOYED IN SAID CRACKING ZONE TO EFFECT REDUCTION OF SAID PHOSPHATE ROCK WITH THE PRODUCTION OF ELEMENTAL PHOSPHORUS. 